Conventionally, there has been known a liquid crystal display device including a liquid crystal panel having three color filters of R (red), G (green), and B (blue) to perform color display. As to the three color filters used in the liquid crystal display device, a gradation-transmittance characteristic is different among the three colors. That is, when attention is given to a certain gradation value, transmittances of light when a voltage corresponding to the relevant gradation value is applied to a liquid crystal layer are different among the three colors. Consequently, in order to make the difference in the transmittance among the three colors small, generally, a structure called a “multi-gap structure” is employed, in which a thickness of the liquid crystal layer differs among the three colors. In the liquid crystal display device employing the multi-gap structure, for example, “R<G<B” holds as to thicknesses of the color filters so that “R>G>B” holds as to the thicknesses of the liquid crystal layer.
In the liquid crystal display device such as a liquid crystal television and the like, a white shade may differ depending on devices due to production variation in color shade of a backlight or the liquid crystal panel. Consequently, in generally, a parameter (a white balance parameter) differing on a device base is used to perform white balance adjustment, whereby the color shade of the liquid crystal display device as a product is kept constant. The white balance adjustment is to adjust a maximum value of an output value to the panel, and the white balance parameter is determined for each color of R, G, and B. At this time, improving balance among R, G, and B offsets the production variation in color shade of the backlight or the liquid crystal panel, and the color shade is kept constant, as described above.
Here, the white balance adjustment will be described. In the white balance adjustment, correction is applied for each of the colors to a value (a gradation value) of gradation data included in an input image signal, so that white is properly displayed regardless of a color temperature of a backlight light source, for example. In order to perform this correction, a lookup table (hereinafter, referred to as a “white balance adjustment LUT”) as shown in FIG. 17, for example, is provided. As shown in FIG. 17, in the white balance adjustment LUT, input gradation values and gradation values after correction for the respective R, G, and B (gradation values after white balance adjustment) are associated with one another. For example, a row indicated by reference numeral 91 indicates “the gradation value after correction is set to “247” as to data of R having the input gradation value of “250”, the gradation value after correction is set to “207” as to data of G having the input gradation value of “250”, and the gradation value after correction is set to “250” as to data of B having the input gradation value of “250”. If there exists pixel data in which the input gradation values of R, G, and B are “250”, “255”, and “251”, respectively, the gradation values after correction of the R, G, and B regarding the pixel data are set to “247”, “210”, and “251”, respectively, as shown in FIG. 18. In this manner, the correction of the gradation values is performed based on the white balance parameter determined for each of the colors, whereby white is properly displayed on a screen.
It should be noted that, in connection with the present invention, a technique concerning white balance adjustment in a liquid crystal display device is disclosed in Japanese Patent Application Laid-Open No. 2011-215479. According to the liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 2011-215479, even before a color temperature of a display image becomes stable, performing proper color temperature adjustment allows an image at a color temperature close to a prescribed color temperature to be displayed in a liquid crystal panel.